Position sensors based on a potentiometer are generally used in forming the position data of structures and parts of various vehicles and working machines. Typically, turning the structure of a device turns the potentiometer, thus creating a change in the resistance of an adjustable resistor. A change in the resistance is interpreted as a change in the position of the structure, which in some applications leads to a certain function. For example, in a vehicle a change in the position of the gas pedal has an effect on the gasoline feed system.
In several uses it is very substantial that no malfunctions occur. Because of this, component securing is used in several applications. For example, the movement of a gas pedal can be measured by two or more sensors, in which case the damaging of one sensor does not necessarily lead into a malfunction.
Different solutions have also been developed for condition monitoring of individual potentiometers. One such solution is disclosed in patent publication U.S. Pat. No. 6,184,695, which discloses a diagnostic circuit for a potentiometric sensor. The main principle of the solution according to the publication is that an alternating voltage is supplied to the sliding contact of an adjustable resistor, by means of which the resistance of the sliding contact is determined. On the basis of the resistance value it is possible to monitor the condition of the adjustable resistor. The solution in question is, however, relatively complex and it only reveals the changes in the resistance of the adjustable resistor.